WO2014174857A1

WO2014174857A1 - Fluoroscopic apparatus

Info

Publication number: WO2014174857A1
Application number: PCT/JP2014/050975
Authority: WO
Inventors: 馬場　理香
Original assignee: 株式会社日立メディコ
Priority date: 2013-04-23
Filing date: 2014-01-20
Publication date: 2014-10-30
Also published as: JP2016127870A

Abstract

The present invention obtains high quality tomosynthesis images in real time in a fluoroscopic apparatus using low dose fluoroscopic data. In the present invention, a detector detects X-rays irradiated from an X-ray source and the data obtained is obtained as fluoroscopic images. When an instruction is received from the user during this time, the X-ray source and the detector are moved relative to each other, pre-processing is performed on the fluoroscopic images acquired during this time, and the images are stored. Then, when a specified number has been stored, arithmetic processing is performed on the stored fluoroscopic images to obtain a tomographic image. The tomographic images obtained can be displayed along with the fluoroscopic images.

Description

X-ray fluoroscope

The present invention relates to X-ray fluoroscopy technology, and more particularly to tomographic image (tomosynthesis image) generation technology.

There is an X-ray fluoroscopy device in which an X-ray source and a two-dimensional X-ray detector are arranged facing each other and moved relatively to perform X-ray imaging. In such an X-ray fluoroscopic apparatus, there is a tomosynthesis imaging technique for obtaining a tomogram (tomosynthesis image) by performing addition processing or reconstruction processing on a series of imaging data acquired at different view angles with respect to a subject. Among them, there is a technique for obtaining a tomographic image using low-dose fluoroscopic data acquired by continuously irradiating X-rays (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2005-199062

In tomosynthesis imaging, since addition processing or reconstruction processing is performed on a plurality of imaging data as described above, imaging data with less noise is desirable. Therefore, if the low-dose fluoroscopic data is used as it is, a low-quality image with a poor SN ratio is obtained. In order to improve the S / N ratio of the imaging data, it is necessary to acquire the imaging data with a high dose or to slow down the reading speed with the detector.

In order to acquire high-dose imaging data, it is necessary to prepare a mode for acquiring data at a high dose separately from the acquisition of fluoroscopic data, and to switch to that mode during tomosynthesis imaging. Therefore, a tomographic image cannot be acquired in real time. Further, if the reading speed is slowed down, the imaging time is prolonged. On the other hand, if the imaging time is shortened to a level suitable for clinical use, the imaging pitch becomes rough, and as a result, ripple artifacts appear in the tomographic image, and the image quality deteriorates.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for obtaining a high-quality tomosynthesis image in real time using low-dose fluoroscopic data in an X-ray fluoroscopic apparatus.

In the present invention, a detector detects X-rays irradiated from an X-ray source and obtains a fluoroscopic image. In the meantime, when an instruction is received from the user, the X-ray source and the detector are moved relative to each other, and a pre-processing for removing noise is performed and held on the fluoroscopic image acquired during that time. Then, at a timing at which a predetermined number of tomographic images can be calculated, arithmetic processing is performed on the stored fluoroscopic images to obtain a tomographic image. The obtained tomographic image may be displayed together with the fluoroscopic image.

Specifically, an X-ray source that irradiates the subject with X-rays, a detector that detects X-rays, an operation control unit that relatively moves the X-ray source and the detector, and the detected X-rays A fluoroscopic image acquisition unit that obtains a fluoroscopic image from a line, a preprocessing unit that performs preprocessing for reducing noise on the fluoroscopic image, a holding unit that holds the fluoroscopic image, and an operation on the fluoroscopic image after the preprocessing An X-ray fluoroscopic apparatus characterized by comprising a calculation unit that performs processing and obtains a tomographic image.

According to the present invention, a high-quality tomosynthesis image can be obtained in real time using low-dose fluoroscopic data in an X-ray fluoroscopic apparatus.

(A)-(c) is a schematic block diagram of the X-ray fluoroscopic apparatus of embodiment of this invention. It is a functional block diagram of a control device of an embodiment of the present invention. It is explanatory drawing for demonstrating an example of the input device of embodiment of this invention. It is explanatory drawing for demonstrating the structure specific process of embodiment of this invention. (A) is explanatory drawing for demonstrating the addition method of embodiment of this invention, (b) is explanatory drawing for demonstrating the shift addition method of embodiment of this invention. (A) And (b) is explanatory drawing for demonstrating the display apparatus of embodiment of this invention. It is explanatory drawing for demonstrating the flow of the measurement process of embodiment of this invention. It is a flowchart of the measurement process of embodiment of this invention. It is a flowchart of the modification of the measurement process of embodiment of this invention. It is a flowchart of the modification of the measurement process of embodiment of this invention.

Hereinafter, embodiments to which the present invention is applied will be described. Hereinafter, in all the drawings for explaining the embodiments of the present invention, those having basically the same function are denoted by the same reference numerals unless otherwise specified, and repeated explanation thereof is omitted.

In this embodiment, a fluoroscopic image and a tomosynthesis image (tomographic image) are obtained by low-dose irradiation. A schematic configuration diagram of an X-ray fluoroscopic apparatus for realizing this is illustrated in FIGS. The X-ray

fluoroscopic apparatuses

110, 120, and 130 of this embodiment include an X-ray tube 100 including an X-ray source 101 that irradiates a subject with X-rays, a detector 102 that detects X-rays, a control device 103, and an arm. 108 and a moving device 109. In the figure, reference numeral 105 denotes a bed on which the subject 104 is mounted. The X-ray source 101 in the X-ray tube 100 and the detector 102 are connected to the moving device 109 by an arm 108.

In the X-ray

fluoroscopic apparatuses

110 and 130 shown in FIGS. 1A and 1C, the arm 108 has a C-shape, and the X-ray source 101 and the detector 102 have a rotation axis on the paper surface. Rotate and move on a circular orbit around 106. In addition, in the X-ray

fluoroscopic apparatuses

110 and 130 of FIG. 1 (a) and (c), the shape of an arm is not restricted to C shape. It may be U-shaped or U-shaped.

In the X-ray fluoroscopic apparatus 120 shown in FIG. 1B, the X-ray source 101 and the detector 102 are installed on separate arms 108, respectively. In the X-ray fluoroscopic apparatus 120, the X-ray source 101 and the detector 102 perform translation, rotation, rotation, and translation. For example, the X-ray source 101 and the detector 102 move in a direction perpendicular to the paper surface parallel to the bed 105 or the floor surface. Alternatively, it moves on a circular orbit around the rotation axis 106 on the paper surface. Alternatively, the X-ray source 101 moves in a direction perpendicular to the paper surface parallel to the bed 105 or the floor surface, and the detector 102 moves on a circular orbit around the rotation axis 106 on the paper surface. Alternatively, the X-ray source 101 moves on a circular orbit around the rotation axis 106 on the paper surface, and the detector 102 moves in a direction perpendicular to the paper surface parallel to the bed 105 or the floor surface.

In the X-ray

fluoroscopic apparatuses

110 and 120 shown in FIGS. 1A and 1B, the subject 104 is arranged so that the body axis thereof is orthogonal to the rotation axis 106. For this reason, the rotatable angle range becomes narrower than 180 degrees. On the other hand, in the X-ray fluoroscopic apparatus 130 shown in FIG. 1C, the subject 104 has its body axis arranged parallel to the rotation axis 106. Therefore, the rotatable angle range is widened, and the image quality of the cross-sectional image is improved. In addition, since the X-ray source 101 and the detector 102 can rotate on the side surface of the subject 104 and a perspective image seen from the side surface of the subject 104 can be obtained, a good cross-sectional image seen from the side surface direction can be obtained. it can.

Note that there are various possible positional relationships between the body axis of the subject 104 and the rotation axis 106. Further, the distance between the bed 105 and the X-ray source 101 and the detector 102 may be closer than the distances shown in FIGS. Further, the X-ray source 101 and the detector 102 may be configured to move on different circular orbits. Further, the external shape of the X-ray fluoroscopic apparatus is not limited to that shown in FIGS. Further, the X-ray source 101 and the detector 102 are not limited to rotation and translation, and may move on any orbit.

In each X-ray

fluoroscopic apparatus

110, 120, 130, X-ray generation in the X-ray source 101, X-ray detection in the detector 102, and movement control of the X-ray source 101 and the detector 102 are performed in the control apparatus 103. Is called. For example, when receiving an instruction to start measurement, the control device 103 causes the X-ray source 101 to emit pulsed X-rays. At the same time, the detector 102 is controlled to detect X-rays in synchronization with pulse X-rays. Then, the X-ray detected by the detector 102 is converted into an electrical signal corresponding to the intensity to obtain a measurement elephant, and a fluoroscopic image is obtained. At this time, the intensity of the pulse X-ray is set to a low dose that does not cause harm even if the subject 104 is continuously irradiated. The control device 103 according to the present embodiment further performs various processes (image processing) on the fluoroscopic image.

Although not shown in FIGS. 1A to 1C, a display device, a storage device, and an input device are connected to the control device 103.

The detector 102 is a two-dimensional detector. In this embodiment, one-dimensional detectors arranged in multiple rows are also included in the two-dimensional detector. Examples of the two-dimensional detector include a planar X-ray detector, a combination of an X-ray image intensifier and a CCD camera, an imaging plate, a CCD detector, and a solid state detector. As a flat type X-ray detector, there is a combination of an amorphous silicon photodiode and a TFT, which are arranged on a square matrix and directly combined with a fluorescent plate. A film may be used as a detector, and this may be read out with a film digitizer to obtain a measurement image.

As described above, the X-ray source 101 and the detector 102 are not limited to the above-described trajectory, and may move on any trajectory. In that case, the control device 103 performs processing for correcting the trajectory of the X-ray source 101 and the detector 102 into a trajectory at the time of translation or a concentric circle, and a tomographic image such as addition processing or reconstruction processing described later is obtained. Arithmetic processing for obtaining is performed. This makes it possible to acquire a tomosynthesis image using images taken in various trajectories.

In this embodiment, as described above, a fluoroscopic image and a tomosynthesis image are obtained with a low dose. For this reason, in this embodiment, pre-processing is performed on a fluoroscopic image acquired at a low dose to reduce noise. A tomogram (tomosynthesis image) is generated using a perspective image with reduced noise. This realizes a tomosynthesis image with good image quality even at a low dose.

The function of the control device 103 of this embodiment that realizes this will be described. FIG. 2 is a functional block diagram of the control device 103 of the present embodiment. Note that an input device 310, a storage device 320, and a display device 330 are connected to the control device 103. The display device 330 displays various images and data generated by the control device 103. The storage device 320 stores various images and data generated by the control device 103. In addition, the input device 310 receives an instruction from the user to the control device 103. Note that the input device 310 may be shared by the display device 330.

The control apparatus 103 according to the present embodiment includes a measurement control unit 301 that irradiates pulse X-rays from the X-ray source 101 and detects X-rays in synchronization with the pulse X-rays by the detector 102, and the X-ray source 101 and detector. An operation control unit 302 that relatively moves the image 102, a fluoroscopic image acquisition unit 303 that obtains a fluoroscopic image from the X-rays detected by the detector 102, and a preprocessing unit that performs preprocessing for reducing noise on the fluoroscopic image 304, a holding unit 305 that holds the fluoroscopic image in the fluoroscopic image holding unit 321, a calculation unit 306 that performs arithmetic processing on the pre-processed fluoroscopic image to obtain a tomographic image, and the fluoroscopic image and the tomographic image in the display device 330 A display control unit 307 for displaying.

Each part of the control device 103 is realized by a CPU provided in the control device 103 loading a program stored in the storage device 320 in advance into the memory and executing the program. The perspective image holding unit 321 is constructed in the storage device 320.

When the measurement control unit 301 receives an instruction to start measurement from the user via the input device 310, the measurement control unit 301 irradiates the X-ray source 101 with pulse X-rays until an end instruction is received. At the same time, the detector 102 detects X-rays in synchronization with the pulse X-rays.

The fluoroscopic image acquisition unit 303 converts the X-rays detected by the detector 102 into an electrical signal corresponding to the intensity every predetermined period, obtains a measurement image, performs sensitivity correction, and obtains a fluoroscopic image. The timing at which the fluoroscopic image acquisition unit 303 acquires a fluoroscopic image is predetermined as a frame rate f. That is, a fluoroscopic image is acquired every 1 / f seconds. The frame rate f may be configured to be settable by the user via the input device 310.

When the operation control unit 302 receives a tomogram (tomosynthesis image) acquisition instruction from the user via the input device 310, the operation control unit 302 moves the measurement system including the X-ray source 101 and the detector 102 until an end instruction is received. Let Specifically, an instruction is given to the moving device 109 to move the X-ray source 101 and the detector 102 relatively. The moving range (moving angle) and moving speed between the X-ray source 101 and the detector 102 are determined in advance. Alternatively, the moving range and the moving speed may be configured to be set by the user via the input device 310.

In this embodiment, imaging for acquiring a tomographic image is referred to as tomosynthesis imaging. In addition, imaging for obtaining a fluoroscopic image is referred to as fluoroscopic imaging. The control device 103 performs fluoroscopic imaging after receiving a measurement start instruction from the user until receiving a measurement end instruction, and during that time, after receiving a tomographic image acquisition instruction from the user, Until accepting, both fluoroscopic imaging and tomosynthesis imaging are performed in parallel.

Here, an outline of the input device 310 that is instructed by the user will be described. In general, the fluoroscopic apparatus is called a control console. FIG. 3 is an explanatory diagram for explaining an example of the input device 310 of the present embodiment. The input device 310 includes an imaging button 311 that receives a measurement start (perspective imaging start) and end instruction from a user, and a changeover switch 312 that receives a tomosynthesis imaging start and end instruction. The changeover switch 312 is a button, lever, foot button, or the like. In addition, the imaging button 311 and the changeover switch 312 may be icons on the touch panel when the display device 330 includes a touch panel.

The pre-processing unit 304 performs noise reduction processing for reducing noise as pre-processing on the fluoroscopic image acquired by the fluoroscopic image acquiring unit 303. In the present embodiment, preprocessing is performed on the fluoroscopic image acquired while the operation control unit 302 moves the measurement system. As noise reduction processing performed as preprocessing, for example, smoothing processing is performed. Various known smoothing processes can be used for the smoothing process. In this embodiment, the imaging target is an area inside the subject 104, and the obtained fluoroscopic image includes a structural part such as a blood vessel and a flat part such as an organ. In the pre-processing of this embodiment, the structure area in the fluoroscopic image and other areas are discriminated, and smoothing processing is performed only on the other area (flat area in the fluoroscopic image) to remove random noise. To do.

∙ Edge extraction processing is used for structure extraction. For example, a differential filter is applied to the fluoroscopic image to extract the structure. Then, smoothing processing is performed on the area other than the structure. As the smoothing process, for example, an averaging process using an averaging filter, an addition averaging process using a weighted averaging filter, or the like is performed.

Smoothing processing may be performed in the time direction instead of the spatial direction. You may go in both directions. When performing in the time direction, the structural region and other regions are specified by taking a difference from the fluoroscopic images acquired immediately before or immediately after. FIG. 4 is a diagram for explaining processing in the case where a difference is taken in the time direction to specify a structure area and other areas.

It is assumed that the fluoroscopic image 410 is acquired at time t0, and thereafter the fluoroscopic image 410 is acquired every Δt. When the fluoroscopic image 410 is acquired at time t0 + Δt, the preprocessing unit 304 obtains a differential image 411 by performing difference processing between the fluoroscopic image 410 acquired at time t0 and held in the fluoroscopic image holding unit 321. . Note that the fluoroscopic image 410 held at the fluoroscopic image holding unit 321 and acquired at time t0 is a fluoroscopic image after preprocessing. Then, a pixel area whose difference value is equal to or smaller than a predetermined threshold, that is, an area where the change is small in the difference image and the movement is small is set as the other area 421, and the area where the difference value is larger than the predetermined threshold has a characteristic structure. Therefore, the structure area 422 is identified. Then, smoothing processing is performed for other regions. Specifically, for each pixel value in the other region 421, an average is calculated for each pixel value between the immediately preceding or immediately following fluoroscopic images. It should be noted that each pixel in the structure area 422 has a value as it is.

As the fluoroscopic image 410 acquired immediately before, the one held in the fluoroscopic image holding unit 321 is used. In addition, when taking a difference from the fluoroscopic image 410 acquired immediately after, it is temporarily held in the fluoroscopic image holding unit 321, and processing is performed when the next fluoroscopic image 410 is held in the fluoroscopic image holding unit 321. .

The holding unit 305 holds a fluoroscopic image while the operation control unit moves the X-ray source 101 and the detector 102. That is, the holding unit 305 stores the pre-processed fluoroscopic image in the fluoroscopic image holding unit 321 of the storage device 320 every time the fluoroscopic image acquisition unit 303 obtains a fluoroscopic image during tomosynthesis imaging. At this time, the movement range and movement speed of the measurement system and the position information of the X-ray source 101 are stored in association with each other. A measurement angle is used for the position information of the X-ray source 101. The measurement angle is, for example, that of the X-ray source 101 when the X-ray source 101 and the detector 102 exist on a line orthogonal to the bed 105 with the origin at the intersection of a straight line group connecting the X-ray source 101 and the detector 102. The coordinate system is defined with a position of 0 degree.

The calculation unit 306 calculates a tomosynthesis image (tomographic image) using the pre-processed fluoroscopic image held in the holding unit 305 at the time of tomosynthesis imaging. For the calculation of the tomographic image, arithmetic processing such as an addition method, a shift addition method, a filter-corrected back projection method or the like is used.

Here, the principle of the addition method at the time of tomosynthesis imaging will be described using FIG. 5 (a) and FIG. 5 (b). For example, when the X-ray fluoroscopy apparatus 120 shown in FIG. 1B is used, generally, during tomosynthesis imaging, the X-ray source 101 and the detector 102 are moved synchronously in opposite directions in parallel to the bed 105. Let Then, the fluoroscopic images detected at the positions of the detectors 102 are added to obtain a tomographic image. This method is called an addition method.

As shown in FIG. 5 (a), when the X-ray source 101 and the detector 102 are moved in opposite directions, the focal point is focused only on one surface 910 parallel to the moving direction, and the focal point is not focused on the other surface. When the obtained fluoroscopic images are added, the structure of the out-of-focus surface is blurred and invisible, and only the structure on the in-focus surface is emphasized. As a result, a cross-sectional image (tomographic image) of the focused position (cross-section 910) is obtained.

In tomosynthesis imaging, the position of the focused surface 910 can be changed by changing the moving speed of the X-ray source 101 and the detector 102. Further, when a flat panel detector is used as the detector 102, the position of the focusing surface 910 can be arbitrarily changed by shifting the element position of the detector 102 when adding, instead of the moving speed. .

For example, as shown in FIG. 5A, a flat panel detector having three detection elements in the moving direction is assumed. The X-ray beam to the center detection element is indicated by a solid line, and the X-ray beam to the leftmost detection element is indicated by a dotted line. Each X-ray beam is focused on a plane 910 indicated by a solid line. When the obtained perspective images are added, a cross-sectional image of the surface 910 is obtained.

Note that, as shown in FIG. 5B, there is a method called a shift addition method for shifting the element position at the time of addition. In the shift addition method, the value of the leftmost element is detected in the fluoroscopic image obtained with the detector 102 positioned on the left side, and the value of the central element is detected in the fluoroscopic image obtained with the detector 102 positioned in the center. In the perspective image obtained with the device 102 positioned on the right side, the value of the rightmost element is added. The X-ray beam to each element to be added is focused on a surface 920 indicated by a solid line. Thus, by shifting the element position at the time of addition, it is possible to obtain a cross-sectional image (tomographic image) at a position different from the focal plane 910 by the addition method shown in FIG.

In addition, when the addition method and the shift addition method are used for the calculation for obtaining a tomographic image, the measurement system (the X-ray source 101 and the detector 102 need to move in parallel trajectories. X-ray fluoroscopy shown in FIG. In the case of an apparatus in which the measurement system moves in parallel, such as the apparatus 120, the obtained fluoroscopic image is used as it is, whereas the

X-ray fluoroscopic apparatuses

110 and 130 shown in FIGS. In the case of an apparatus in which the measurement system rotates, the obtained fluoroscopic image is converted into a fluoroscopic image detected at the detection position in the parallel orbit by a geometric conversion process.

Tomographic images can be acquired at high speed by using the addition method and shift addition method for the arithmetic processing.

Next, the principle of the filtered back projection method will be described. In the filtered back projection method, the measurement system rotates on a concentric orbit. That is, the measurement system is rotated to obtain a perspective image at each predetermined measurement angle, and a reconstruction process is performed on the perspective image obtained at each measurement angle to obtain a tomographic image as a reconstruction image. In the reconstruction process, an addition process is performed after applying a reconstruction filter to the fluoroscopic image obtained at each measurement angle. According to the filtered back projection method, adding the values of the elements on which an X-ray beam passing through an arbitrary pixel on the reconstructed image is added, the structure reflected in the fluoroscopic image at all angles is emphasized because it is in focus. A structure that appears only in a perspective image at a certain angle is blurred and cannot be seen because it is out of focus. Thereby, a tomographic image of a desired cross section can be obtained.

It should be noted that a tomographic image with little blur and high contrast can be acquired by using the filter-corrected back projection method for the arithmetic processing. However, the filter-corrected backprojection method can be applied to a fluoroscopic image obtained by an X-ray fluoroscopic apparatus in which a measurement system moves on a rotating trajectory. A fluoroscopic image obtained by an X-ray fluoroscopic apparatus in which a measurement system moves in a parallel trajectory is converted into a fluoroscopic image detected at a detection position on a rotational trajectory by a geometric conversion process.

It should be noted that a predetermined number of fluoroscopic images acquired at different measurement angles are required even when a tomographic image is created by any of the addition method, shift addition method, and filter-corrected back projection method. The calculation unit 306 performs calculation processing each time a predetermined number of fluoroscopic images are held in the holding unit while the operation control unit 302 moves the X-ray source 101 and the detector 102. In the present embodiment, the calculation unit 306 performs calculation processing after confirming that a predetermined number of fluoroscopic images acquired at different measurement angles are held in the fluoroscopic image holding unit 321. As described above, the fluoroscopic image holding unit 321 holds a fluoroscopic image in association with the measurement angle. Therefore, for example, when a fluoroscopic image of all measurement angles within a preset movement range of the measurement system is held, the calculation unit 306 starts calculation processing.

The display control unit 307 displays at least one of the obtained fluoroscopic image and tomographic image on the display device 330. In the present embodiment, at the time of fluoroscopic imaging, the acquired fluoroscopic image is displayed on the display device 330 in real time. On the other hand, during tomosynthesis imaging, a fluoroscopic image and a tomographic image are displayed in parallel. Alternatively, only a tomographic image is displayed or a fluoroscopic image and a tomographic image are displayed in accordance with an instruction from the user.

6A and 6B show display examples by the display control unit 307 of the present embodiment. The display device 330 includes an image display area 200. As shown in FIG. 6A, the image display area 200 includes a first display area 210 and a second display area 220. For example, a fluoroscopic image is displayed only in one of the first display area 210 and the second display area 220 during fluoroscopic imaging. On the other hand, during tomosynthesis imaging, a fluoroscopic image is displayed on one of the first display area 210 and the second display area 220, and a tomographic image is displayed on the other.

Further, it may be configured to acquire tomographic images of a plurality of cross sections, display an image obtained by superimposing a fluoroscopic image and one tomographic image in one of the regions, and display a tomographic image of the other cross section in the other region. Good. At this time, the tomographic image displayed in the other region may be a tomographic image having a cross section in a different direction from the tomographic image superimposed on the fluoroscopic image.

The display device 330 may further include a display change instruction button 230. The display control unit 307 receives a change in the display layout of the image display area 200 using the display change instruction button 230. For example, the layout can be changed between a layout in which two

display areas

210 and 220 are displayed in parallel as shown in FIG. 6A and a layout of only one display area 210 as shown in FIG. 6B. .

For example, at the time of fluoroscopic imaging, a fluoroscopic image is displayed in the layout of one display area 210 as shown in FIG. 6B, and at the time of tomosynthesis imaging, two

display areas

210 and 220 are shown as shown in FIG. 6A. A fluoroscopic image and a tomographic image may be displayed in parallel in a layout including Further, even during tomosynthesis imaging, only a tomographic image may be displayed using a layout of only one display area 210 as necessary.

Next, the flow of measurement processing of this embodiment will be described. First, an outline will be described with reference to FIG. When an instruction to start measurement is received, the measurement control unit 301 starts X-ray irradiation and detection, and starts fluoroscopic imaging. In the fluoroscopic imaging, the fluoroscopic image acquisition unit 303 acquires a fluoroscopic image at a timing determined by the frame rate f, and the display control unit 307 displays it on the display device 330. This is executed until an instruction to end measurement is received. In FIG. 7, the timing at which a fluoroscopic image is acquired and displayed (updated) is indicated by a black circle.

During this time, upon receiving an instruction to start tomosynthesis imaging, the operation control unit 302 moves the measurement system. The pre-processing unit 304 performs pre-processing on the acquired fluoroscopic image every time the fluoroscopic image acquiring unit 303 acquires the fluoroscopic image. Then, the holding unit 305 holds the pre-processed fluoroscopic image in the fluoroscopic image holding unit 321. The arithmetic unit 306 performs arithmetic processing when a predetermined number of fluoroscopic images are held, and generates a tomographic image. The display control unit 307 updates the fluoroscopic image displayed in the first display area 210 every time a new fluoroscopic image is acquired, and displays it in the second display area 220 every time a new tomographic image is acquired. Update the tomographic image. In FIG. 7, the timing at which the tomographic image is calculated and displayed (updated) is indicated by a black triangle. Here, a case where a tomographic image is calculated from four perspective images is illustrated. During this time, the measurement control unit 301 and the fluoroscopic image acquisition unit 303 continue the above processing.

Note that tomosynthesis imaging can be performed any number of times during fluoroscopic imaging.

FIG. 8 is a processing flow of the imaging process of the present embodiment. This process starts when a measurement start instruction is received from the user. As described above, in this embodiment, when an instruction for tomosynthesis imaging is received from the user, tomosynthesis imaging is also executed in a state where fluoroscopic imaging is executed.

The measurement control unit 301 activates the measurement system and starts measurement (step S1001). Here, irradiation of pulse X-rays from the X-ray source 101 is started, and X-rays are detected by the detector 102 in synchronization with the pulse X-rays. Next, the operation control unit 302 determines whether an instruction to start tomosynthesis imaging (TOMO start) has been received (step S1002).

In step S1002, if not received, the fluoroscopic image acquisition unit 303 obtains a fluoroscopic image from the X-rays detected by the detector 102 (step S1003). Then, the display control unit 307 displays the fluoroscopic image in the image display area 200 of the display device 330 (step S1004). If the perspective image is displayed first, the display is updated to a new perspective image. Thereafter, the measurement control unit 301 determines whether or not an instruction to end measurement has been received (step S1005). If it has been received, the X-ray irradiation and detection are ended, and the measurement is ended. On the other hand, if not received, the process returns to step S1002.

In step S1002, when receiving an instruction to start tomosynthesis imaging, the operation control unit 302 causes the measurement system to start a moving operation (step S1006). Then, the fluoroscopic image acquisition unit 303 obtains a fluoroscopic image from the X-rays detected by the detector 102 (step S1007). The display control unit 307 displays the fluoroscopic image in the first display area 210 of the display device 330 (step S1008). If the fluoroscopic image is displayed first, the display is updated to the new fluoroscopic image acquired here.

The preprocessing unit 304 performs preprocessing on the acquired fluoroscopic image (step S1009). Here, smoothing processing may be performed in the time direction between the fluoroscopic image held in the holding unit 305 immediately before. In this case, the structure area is specified by the difference, and the smoothing process is performed on the other areas. In addition, a structure may be extracted by means such as a differential filter in one perspective image, and spatial smoothing may be performed.

The holding unit 305 holds the pre-processed fluoroscopic image in the fluoroscopic image holding unit 321 (step S1009). At this time, the fluoroscopic image is stored in association with the position information of the X-ray source 101 at the time when the fluoroscopic image is acquired.

The calculating unit 306 determines whether or not a predetermined number of fluoroscopic images are held in the holding unit 305 (step S1011). The determination may be performed based on the number of sheets, or may be performed based on whether or not the X-ray source 101 has moved the entire predetermined movement range. If not, the process returns to step S1007 to repeat the process.

On the other hand, if it is held, the calculation unit 306 performs a calculation process on the fluoroscopic image held in the holding unit 305 to calculate a tomogram (tomosynthesis image) (step S1012). The arithmetic process may be any process that obtains a tomosynthesis image, such as an addition process, a shift addition process, or a reconstruction process. Then, the display control unit 307 displays the obtained tomographic image on the second display area 220 of the display device 330 (step S1013). If the tomographic image is displayed first, the display is updated to the new tomographic image acquired here. At this time, the first fluoroscopic image obtained at that time is displayed in the first display area 210. However, when an instruction to display only a tomographic image is received from the user, the instruction is displayed on the display device 330 according to the instruction from the user.

Next, the operation control unit 302 determines whether an instruction to end tomosynthesis imaging (TOMO end) has been received from the user (step S1014). If it has been received, the moving operation is terminated, and the process proceeds to step S1005. On the other hand, if not received, the process proceeds to step S1007 and the process is continued.

As described above, the X-ray fluoroscopic apparatus of this embodiment includes the X-ray source 101 that irradiates the subject 104 with X-rays, the detector 102 that detects X-rays, the X-ray source 101, and the detector 102. An operation control unit 302 that relatively moves the fluoroscopic image acquisition unit 303 that obtains a fluoroscopic image from the detected X-ray, a preprocessing unit 304 that performs preprocessing for reducing noise on the fluoroscopic image, A holding unit 305 that holds a fluoroscopic image, and a calculation unit 306 that performs arithmetic processing on the fluoroscopic image after the preprocessing and obtains a tomographic image.

As described above, when receiving an instruction for tomosynthesis imaging, the X-ray fluoroscopic apparatus of the present embodiment holds fluoroscopic data (fluoroscopic image) obtained at a low dose, and before removing noise from the held fluoroscopic image. Apply processing. Then, a tomographic image is generated using the perspective image after removing the noise. By performing preprocessing, a high-quality tomographic image with less noise can be obtained from a perspective image with relatively large noise acquired at a low dose. That is, according to the present embodiment, it is possible to obtain a high-quality tomosynthesis image in real time using low-dose fluoroscopic data.

As described above, according to the present embodiment, a tomographic image is also obtained by tomosynthesis imaging while performing fluoroscopic imaging. Therefore, according to the present embodiment, a fluoroscopic image and a tomographic image can be obtained in parallel. At this time, the X-ray fluoroscopic apparatus of the present embodiment further includes a display device 330 that displays the fluoroscopic image and the tomographic image. The display device 330 displays the fluoroscopic image and one or more tomographic images side by side.

Thus, for example, in catheterization, the depth position of the catheter tip can be quickly confirmed and reflected in the surgery. Since the depth position of the subject of interest can be confirmed without stopping the operation, the operation time can be shortened and the exposure of the patient and the operator can be reduced. In addition, the fluoroscopic image and the tomosynthesis image can be displayed in real time and can be used as an intraoperative navigation map.

In the above embodiment, the pre-processing is performed on the fluoroscopic image only when an instruction for tomosynthesis imaging is received, but the present invention is not limited to this. You may comprise so that it may pre-process with respect to the said fluoroscopic image whenever it acquires a fluoroscopic image. That is, preprocessing is always performed on the acquired fluoroscopic image before display. The flow of the imaging process in this case is shown in FIG.

When the measurement control unit 301 receives an instruction to start measurement from the user, the measurement control unit 301 activates the measurement system and starts measurement (step S1101). Here, irradiation of pulse X-rays from the X-ray source 101 is started, and X-rays are detected by the detector 102 in synchronization with the pulse X-rays. Next, the operation control unit 302 determines whether or not an instruction to start tomosynthesis imaging (TOMO start) has been received (step S1102).

In step S1102, if not received, the fluoroscopic image acquisition unit 303 obtains a fluoroscopic image from the X-rays detected by the detector 102 (step S1103). Then, the preprocessing unit 304 performs preprocessing on the fluoroscopic image (step S1104). The display control unit 307 displays the fluoroscopic image after the preprocessing in step S1104 in the image display area 200 of the display device 330 (step S1106). If the perspective image is displayed first, the display is updated to a new perspective image. Thereafter, the measurement control unit 301 determines whether or not an instruction to end the measurement has been received (step S1107). If the instruction has been received, the X-ray irradiation and detection are ended, and the measurement is ended. On the other hand, if not received, the process returns to step S1102.

In step S1102, when an instruction to start tomosynthesis imaging is received, the operation control unit 302 moves the measurement system (step S1108). Then, the fluoroscopic image acquisition unit 303 obtains a fluoroscopic image from the X-rays detected by the detector 102 (step S1109). The preprocessing unit 304 performs preprocessing on the acquired fluoroscopic image (step S1110). Then, the holding unit 305 holds the fluoroscopic image after the preprocessing in the fluoroscopic image holding unit 321 (step S1111). At this time, the fluoroscopic image is stored in association with the position information of the X-ray source 101 at the time when the fluoroscopic image is acquired. On the other hand, the display control unit 307 displays the fluoroscopic image after the preprocessing in Step S1110 in the first display area 210 of the display device 330 (Step S1112). If the fluoroscopic image is displayed first, the display is updated to the new fluoroscopic image acquired here.

The operation control unit 302 determines whether or not a predetermined number of fluoroscopic images are held in the holding unit 305 (step S1113). The determination may be performed based on the number of sheets, or may be performed based on whether or not the X-ray source 101 has moved the entire predetermined movement range. If not, the process returns to step S1109 to repeat the process.

On the other hand, if it is held, the calculation unit 306 performs a calculation process on the fluoroscopic image held in the holding unit 305 to calculate a tomogram (tomosynthesis image) (step S1114). Then, the display control unit 307 displays the obtained tomographic image together with the fluoroscopic image obtained at that time on the second display area 220 of the display device 330 (step S1115). If the tomographic image is displayed first, the display is updated to the new tomographic image acquired here. In the first display area 210, the latest perspective image is displayed at that time. However, when an instruction to display only a tomographic image is received from the user, the instruction is displayed on the display device 330 according to the instruction from the user.

Next, the operation control unit 302 determines whether an instruction to end tomosynthesis imaging (TOMO end) has been received from the user (step S1116). If it has been received, the moving operation is terminated, and the process proceeds to step S1107. On the other hand, if not received, the process proceeds to step S1109 and the process is continued.

Thus, by performing preprocessing every time a fluoroscopic image is acquired, high-quality images can be obtained and displayed even in normal fluoroscopic imaging. In addition, the processing time when acquiring a tomographic image can be shortened.

It should be noted that the moving speed and moving range (angle) may be configured to be changeable by the user during tomosynthesis imaging. In other words, the X-ray fluoroscopic apparatus of the present embodiment may be configured to accept from the user via the input device 310 settings of at least one of the range in which the X-ray source 101 and the detector 102 are moved and the moving speed. . In order to receive an input, for example, the input device 310 includes a measurement system operation control instruction unit. The operation control unit 302 receives a predetermined operation by the user and changes the moving range and moving speed of the measurement system.

The changeover switch 312 may also serve as the operation control instruction unit. For example, when accepting that the user has pressed the changeover switch 312 more strongly than usual, the operation control unit 302 expands the movement range. In addition, when accepting that the user has moved the changeover switch 312 earlier than usual, the operation control unit 302 increases the moving speed.

Note that the fluoroscopic image acquisition unit 303 according to the present embodiment changes the time interval for acquiring the fluoroscopic image specified by the frame rate f according to the setting when receiving an instruction to change the moving speed and / or moving range from the user. You may comprise. For example, upon receiving an instruction to increase the moving speed of the measurement system, the fluoroscopic image acquisition unit 303 increases the frame rate f for capturing the fluoroscopic image. Artifacts occur when the pitch at which images are acquired becomes coarse, but the occurrence of these artifacts is prevented by changing the frame rate in this way. On the other hand, when an instruction to reduce the moving speed of the measurement system is received, the frame rate is reduced. If the moving speed of the measurement system is slow, the pitch becomes finer than necessary, and the amount of exposure of the subject 104 increases. At this time, by increasing the frame rate, an increase in the amount of exposure of the subject 104 can be suppressed.

Specifically, for example, when the frame rate is set to f (number of sheets / second), the maximum measurement angle of the measurement system is ± (A / 2) degree, and the rotation speed of the measurement system is s (degree / sec). While the measurement system is rotated by the rotation angle A, f × A / s fluoroscopic images are acquired. As the rotation speed s increases, the number of fluoroscopic images acquired while the measurement system rotates by the rotation angle A decreases. Therefore, if the frame rate is increased accordingly, the number of fluoroscopic images acquired while the measurement system is rotated by the rotation angle A can be maintained. It is possible to prevent the image acquisition pitch from becoming coarse. Conversely, when the rotational speed s is slow (small), the number of fluoroscopic images acquired while the measurement system is rotated by the rotational angle A increases. Therefore, by reducing the frame rate, the number of acquired images can be maintained, and an increase in irradiation amount can be suppressed.

In the above-described embodiment, the holding unit 305 is configured to hold the fluoroscopic image in the fluoroscopic image holding unit 321 until receiving an instruction to end tomosynthesis imaging only when receiving an instruction for tomosynthesis imaging from the user. Not limited to this. In response to an instruction to start measurement, X-rays may be emitted from the X-ray source 101 and a fluoroscopic image may be constantly held while X-rays are detected by the detector 102. In this case as well, the position information of the X-ray source 101 is held in correspondence with the embodiment. In this case, only a predetermined number of fluoroscopic images may be retained and overwritten for a predetermined period.

In the above embodiment, the operation control unit 302 moves the measurement system only when receiving an instruction to end tomosynthesis imaging only when receiving an instruction for tomosynthesis imaging from the user, but is not limited thereto. The measurement system may be configured to move in response to an instruction to start measurement. In this case, the operation control unit 302 moves the X-ray source 101 and the detector 102 when X-ray irradiation is started.

It may be configured to always move the measurement system during measurement and hold the fluoroscopic image in the holding unit 305 during fluoroscopic imaging. In this case as well, the position information of the X-ray source 101 is held in correspondence with the embodiment. The flow of the measurement process in this case is shown in FIG. The flow of the measurement process in this case is basically the same as the example shown in FIG. However, in step S1101, the operation control unit 302 starts moving the measurement system. In step S 1107, the measurement end instruction is received, and the measurement type moving operation is ended. Further, even when the instruction for tomosynthesis imaging is not received, after the preprocessing (step S1104), the holding unit 305 holds the fluoroscopic image in the fluoroscopic image holding unit 321 (step S1105).

When the measurement system is always moved and the fluoroscopic image is held in the holding unit 305 during fluoroscopic imaging, the tomosynthesis imaging instruction is given when the fluoroscopic image necessary for tomographic image calculation is already held in the holding unit 305. Can be generated immediately.

In this case, even if an instruction for tomosynthesis imaging is accepted, if a necessary fluoroscopic image is not accumulated in the holding unit 305, a warning may be given to that effect. In addition, the fluoroscopic image held in the holding unit 305 at that time may be displayed on the image display area 200 of the display device 330 and the selection of the fluoroscopic image used for tomographic image generation may be received from the user.

Furthermore, the

X-ray fluoroscopic apparatuses

110, 120, and 130 may have a function capable of adjusting the X-ray dose irradiated from the X-ray source 101. For example, it may be configured so that irradiation with a high dose is possible and normal tomosynthesis imaging is possible.

When provided with a function capable of adjusting the X-ray dose, the storage device 320 holds an image acquired at a low dose and an image acquired at a high dose in a mixed manner. In such a case, when tomosynthesis imaging is instructed, a function for determining whether or not preprocessing is necessary for an image held in the storage device 320 may be provided. The necessity determination is performed, for example, by a method of calculating a standard deviation of pixel values of a region other than the structure of the image to be held and performing no preprocessing when it is smaller than a predetermined threshold. As a result, the number of times of preprocessing is reduced, and the processing time can be shortened.

Note that the X-ray fluoroscopic apparatus of the present embodiment may include a collimator that limits an X-ray irradiation region.

In the above embodiment, the calculation process is performed by the calculation unit 306. However, when the addition method is used for the calculation process, the addition process is performed when the holding unit 305 holds the perspective image in the storage device 320. May be. With this configuration, a tomographic image can be obtained at a higher speed. In this case, the calculation unit 306 may not be provided.

Further, the present embodiment is not limited to tomosynthesis imaging. The present invention can also be applied to imaging for obtaining other types of tomographic images such as CT imaging and cone beam CT imaging. Furthermore, this embodiment is not limited to the measurement by X-rays. Even measurement of light, X-rays, radiation, etc. is applicable.

100: X-ray tube, 101: X-ray source, 102: detector, 103: control device, 104: subject, 105: bed, 106: rotating shaft, 108: arm, 109: moving device, 110: X-ray fluoroscopy device 120: X-ray fluoroscopic apparatus, 130: X-ray fluoroscopic apparatus, 210: First display area, 220: Second display area, 230: Display change instruction button, 301: Measurement control section, 302: Operation control section, 303: perspective image acquisition unit, 304: preprocessing unit, 305: holding unit, 306: calculation unit, 307: display control unit, 310: input device, 311: imaging button, 312: changeover switch, 320: storage device, 321 : Perspective image holding unit, 330: display device, 410: perspective image, 411: difference image, 421: non-structure region, 422: structure region, 910: cross section, 920: cross section

Claims

An X-ray source that irradiates the subject with X-rays;
A detector for detecting X-rays;
An operation controller that relatively moves the X-ray source and the detector;
A fluoroscopic image obtaining unit for obtaining a fluoroscopic image from the detected X-ray;
A preprocessing unit that performs preprocessing for reducing noise with respect to the fluoroscopic image;
A holding unit for holding the fluoroscopic image after pre-processing;
An X-ray fluoroscopic apparatus comprising: an arithmetic unit that performs arithmetic processing on the fluoroscopic image held in the holding unit to obtain a tomographic image.
The X-ray fluoroscopic apparatus according to claim 1,
An X-ray fluoroscopic apparatus, further comprising: a display device that displays the fluoroscopic image and the tomographic image.
The X-ray fluoroscopic apparatus according to claim 1,
The X-ray fluoroscopic apparatus, wherein the holding unit holds the fluoroscopic image obtained while the operation control unit moves the X-ray source and the detector.
The X-ray fluoroscopic apparatus according to claim 1,
The calculation unit performs the calculation process each time a predetermined number of fluoroscopic images are held in the holding unit while the operation control unit moves the X-ray source and the detector. X-ray fluoroscopic apparatus characterized by the above.
The X-ray fluoroscopic apparatus according to claim 1,
The operation control unit moves the X-ray source and the detector according to an instruction from a user.
The X-ray fluoroscopic apparatus according to claim 1,
The operation control unit moves the X-ray source and the detector when X-ray irradiation is started.
The X-ray fluoroscopic apparatus according to claim 1,
The X-ray fluoroscopic apparatus, wherein the preprocessing unit performs the preprocessing on the fluoroscopic image acquired while the operation control unit moves the X-ray source and the detector. .
The X-ray fluoroscopic apparatus according to claim 1,
The X-ray fluoroscopic apparatus, wherein the preprocessing unit performs the preprocessing on the fluoroscopic image every time the fluoroscopic image is acquired.
The X-ray fluoroscopic apparatus according to claim 1,
The X-ray fluoroscopic apparatus, wherein the preprocessing is a smoothing process.
The X-ray fluoroscopic apparatus according to claim 9,
The X-ray fluoroscopic apparatus, wherein the preprocessing unit discriminates a structure area and other areas in the fluoroscopic image and performs the smoothing process only on the other areas.
The X-ray fluoroscopic apparatus according to claim 1,
The X-ray fluoroscopic apparatus, wherein the calculation process is any one of an addition process, a shift addition process, and a filter-corrected backprojection process.
The X-ray fluoroscopic apparatus according to claim 1,
An X-ray fluoroscopic apparatus, further comprising: an input device that accepts a setting of at least one of a range and a moving speed for moving the X-ray source and the detector.
The X-ray fluoroscope according to claim 12,
The fluoroscopic image acquisition unit, when receiving the setting from a user, changes a time interval for acquiring the fluoroscopic image according to the setting.
The X-ray fluoroscopic apparatus according to claim 1,
The operation control unit translates or rotates the X-ray source and the detector.
The X-ray fluoroscopic apparatus according to claim 2,
The X-ray fluoroscopic device, wherein the display device displays the fluoroscopic image and the one or more tomographic images side by side.